http://localhost:8080/tede/handle/tede/4 Mon, 20 Apr 2026 16:17:06 GMT 2026-04-20T16:17:06Z http://localhost:8080/tede/handle/tede/202 GERAÇÃO E CARACTERIZAÇÃO PETROFÍSICA E GEOQUÍMICA DE ROCHAS CARBONÁTICAS SINTERIZADAS COM CONTEÚDO DE MAGNETITA NANOMÉTRICA Jonatã Barbosa Teixeira, Jonatã Barbosa Teixeira Daniel Ribeiro Franco, Daniel Ribeiro Franco The presence of magnetite (Fe3O4) in petroleum systems represents an important factor in understanding inaccuracies related to carbonate formations, which influence both exploration and the petrophysical analysis of these reservoirs. In this doctoral thesis, we investigate the effects of synthesized magnetite, using the co-precipitation method, in various grain sizes and concentrations, exploring its relationship with the pore space in different porosities and the fluid present in the reservoir. The results consist of two main articles. The first article investigates how pH variations induced by acid affect the surface properties and catalytic and leaching activities of nanometric and micrometric magnetites, particularly in the presence of naphthalene. These changes are crucial for chemical decomposition processes in carbonate reservoirs. By analyzing catalytic performance under different pH conditions, the project provides valuable insights into the potential environmental impacts and practical applications of acid fracturing, particularly relevant to Enhanced Oil Recovery (EOR). It was noted that under acidic conditions, the Fe2+ ions leached from magnetite oxidize naphthalene, revealing their crucial role in the chemical decomposition of organic substrates in oil extracted from rocks containing magnetite. It was discovered that the chemical and crystallographic structure of magnetite significantly influences the decomposition of naphthalene, used as a model of Polycyclic Aromatic Hydrocarbon (PAH). Additionally, the morphology of magnetite grains, whether micro or nanometric, plays an important role as a heterogeneous catalyst, along with the acidity of the aqueous medium. Homogeneous catalysts demonstrated greater efficiency in decomposing naphthalene, followed by samples of nanometric and micrometric magnetite, which act as heterogeneous catalysts. The second article employs laboratory methods to investigate the interferences that magnetites may cause in Nuclear Magnetic Resonance (NMR) spectra and consequently in petrophysical estimates based on NMR. Twelve synthetic carbonates with different concentrations of magnetites and varying porosities were prepared, and mineralogical and magnetic characterizations were performed. Furthermore, the study included gas porosimetry analyses and permeability estimation using a permeameter. It was observed that shifts in the T2 spectrum are strongly correlated with increased magnetic susceptibility. The gradient of diffusive relaxation contributed to the overlap of the magnetic susceptibility of carbonates concerning the amount of porosity in samples with higher magnetite concentrations, while in carbonates with lower amounts of magnetite, the surface relaxivity modulated the T2 curve. These results show a strong correlation between the rate of diffusive relaxation and the concentration of magnetite. It is emphasized that to utilize relaxation rates from NMR in estimating porosity and permeability in carbonate rocks, one must consider the effects caused by magnetite. In summary, these studies represent a significant contribution to advancing knowledge in the characterization of magnetic minerals in carbonate formations of petroleum systems, exploring their interaction with pore space, their filling, and enhancing the understanding of pore potential. This provides insights for future research on chemical reactions in the magnetic characterization of carbonates, enhanced oil recovery, and the estimation of porosity and permeability based on T2 spectra. Observatorio Nacional Tese Tue, 29 Apr 2025 00:00:00 GMT http://localhost:8080/tede/handle/tede/202 2025-04-29T00:00:00Z http://localhost:8080/tede/handle/tede/201 “ANÁLISE DE LINHAS DE TRANSMISSÃO DE ENERGIA EM REGIÕES EQUATORIAIS DURANTE A TEMPESTADE GEOMAGNÉTICA DE 10-11 DE MAIO DE 2024” Éfren Mota de Souza, Éfren Mota de Souza Luiz Carlos de Carvalho Benyosef, Luiz Carlos de Carvalho Benyosef Geomagnetically induced currents (GICs) represent an increasing risk to the integrity of electrical power systems, particularly high-voltage transmission lines (TLs). Generated by rapid variations in the geomagnetic field, these currents can penetrate electrical networks through grounded neutral points of substation transformers. This study investigates the relationship between electrical parameters from two TLs in northern Brazil, near the magnetic equator, and magnetic parameters from nearby observatories during the severe geomagnetic storm of 10–11 May 2024. In addition, a comparative analysis, restricted to the statistical procedure, was conducted for a geomagnetically moderate period on 24 March 2024. The analysis included current and voltage data from the TLs and magnetic records (H-component) from the Tatuoca (TTB), Kourou (KOU), and São Luís (SLZ) observatories, with emphasis on the influence of the Equatorial Electrojet (EEJ). The temporal derivative of the horizontal component (dH/dt) was used as an indicator of the intensity of geomagnetic disturbances capable of inducing GICs, while Pearson’s correlation coefficient quantified the relationships between electrical and magnetic variables. The results revealed dH/dt peaks exceeding 60 nT/min at TTB and SLZ, particularly at the sudden commencement of the storm (17:05 UTC), associated with the arrival of a Coronal Mass Ejection (CME). KOU, being the observatory farthest from the EEJ influence, displayed the lowest peak among all. An increase in dH/dt with proximity to the magnetic equator was observed, highlighting the role of the EEJ. A threshold value of 30 nT/min (associated with the risk of inducing GICs) was exceeded multiple times at all magnetic observatories during the analyzed period. Correlations were strong to very strong (r > |0.80|) during the initial and main phases of the storm, and weaker to moderate durin g the recovery phase (|0.39| ≤ r ≤ |0.55|), revealing phase-dependent patterns. Comparison with the moderate period (24 March 2024) indicated similar r patterns between current and H-component to those observed during the initial and main storm phases (r < –0.91), but weak and inverse correlations between H-component and voltage (–0.10 ≤ r ≤ –0.16). Although preliminary, these results emphasize the importance of regional factors in GIC risk assessment and demonstrate the potential of integrating raw electrical TL data with geomagnetic observations for preventive strategies in power systems. Observatorio Nacional Dissertação Tue, 07 Oct 2025 00:00:00 GMT http://localhost:8080/tede/handle/tede/201 2025-10-07T00:00:00Z http://localhost:8080/tede/handle/tede/199 “ANÁLISE CICLOESTRATIGRÁFICA DOS DEPÓSITOS SEDIMENTARES DA BACIA POTIGUAR DURANTE O INTERVALO CENOMANIANO-TURONIANO” Evelyn Paiva do Nascimento, Evelyn Paiva do Nascimento Daniel Ribeiro Franco , Daniel Ribeiro Franco Exploratory sedimentary basins require continuous chronostratigraphic refinement. However, in continental settings, this remains challenging due to the complex and dynamic erosional processes of fluvial and fluvio-estuarine systems, which often obscure the depositional record. Consequently, investigating the influence of orbital cycles - an approach that can aid in refining chronostratigraphic frameworks - in these records is also a challenge. As a result, studies on this topic are relatively uncommon in the literature, despite the growing recent interest from the scientific community. In this context, the fluvio-estuarine deposits of the Açu Formation, in the Potiguar Basin - an important exploratory basin located on the Brazilian equatorial margin - represent an special sedimentary archive in which T-R cycles can be traced laterally for tens of kilometers. This makes them an interesting subject for cyclostratigraphic analysis in non-marine environments. This study investigates the influence of orbital forcing on the Açu Formation, correlate cycles influenced by orbital variations in the wells, and establish the preserved time interval through the construction of an Astronomical Time Scale (ATS). Cyclostratigraphic analyses were performed using time series techniques on gamma-ray logging data from three wells, focusing on two third-order sequences deposited from the Cenomanian-Turonian boundary (approximately 101 to 93 million years ago). Statistical methods including correlation coefficient (COCO) and the null hypothesis (H0), were applied to determine the ideal sedimentation rate (SAR) and test the record of astronomical cycles. The Integrated Error Prediction Filter Analysis (INPEFA) was used to identify trends in the sedimentary record, improving the correlation of matching cycles. The cyclostratigraphic results demonstrate the imprint of orbital forcing on the sedimentary deposits, consistent with the astronomical solutions for the Cenomanian-Turonian interval. The inferred sedimentation rates range from approximately 3 to 8 cm/kyr, consistent with similar depositional environments. The identification of spectral bands corresponding to the long eccentricity cycle (405 ka) allowed for the construction of a floating ATS for the Cenomanian-Turonian interval in the basin and the estimation of the recorded time. Since the good preservation of orbital signals in fluvio-estuarine environments is uncommon - limiting the number of cycle-stratigraphic studies - this research provides important insights into the behavior of orbital signals and basin filling in this type of paleoenvironment. Furthermore, as this interval includes hydrocarbon-bearing deposits, the findings contribute to the advancement of cyclostratigraphic studies in exploratory basins, with potential applications for chronostratigraphic correlation. Observatorio Nacional Dissertação Fri, 13 Jun 2025 00:00:00 GMT http://localhost:8080/tede/handle/tede/199 2025-06-13T00:00:00Z http://localhost:8080/tede/handle/tede/198 “ANÁLISE DE LINHAS DE TRANSMISSÃO DE ENERGIA EM REGIÕES EQUATORIAIS DURANTE A TEMPESTADE GEOMAGNÉTICA DE 10-11 DE MAIO DE 2024 Éfren Mota de Souza Carvalho Benyosef, Luiz Carlos Abstract ANALYSIS OF ELECTRICAL POWER TRANSMISSION LINES IN EQUATORIAL REGIONS DURING THE GEOMAGNETIC STORM OF 10–11 MAY 2024 Éfren Mota de Souza October 2025 Geomagnetically induced currents (GICs) represent an increasing risk to the integrity of electrical power systems, particularly high-voltage transmission lines (TLs). Generated by rapid variations in the geomagnetic field, these currents can penetrate electrical networks through grounded neutral points of substation transformers. This study investigates the relationship between electrical parameters from two TLs in northern Brazil, near the magnetic equator, and magnetic parameters from nearby observatories during the severe geomagnetic storm of 10–11 May 2024. In addition, a comparative analysis, restricted to the statistical procedure, was conducted for a geomagnetically moderate period on 24 March 2024. The analysis included current and voltage data from the TLs and magnetic records (H-component) from the Tatuoca (TTB), Kourou (KOU), and São Luís (SLZ) observatories, with emphasis on the influence of the Equatorial Electrojet (EEJ). The temporal derivative of the horizontal component (dH/dt) was used as an indicator of the intensity of geomagnetic disturbances capable of inducing GICs, while Pearson’s correlation coefficient quantified the relationships between electrical and magnetic variables. The results revealed dH/dt peaks exceeding 60 nT/min at TTB and SLZ, particularly at the sudden commencement of the storm (17:05 UTC), associated with the arrival of a Coronal Mass Ejection (CME). KOU, being the observatory farthest from the EEJ influence, displayed the lowest peak among all. An increase in dH/dt with proximity to the magnetic equator was observed, highlighting the role of the EEJ. A threshold value of 30 nT/min (associated with the risk of inducing GICs) was exceeded multiple times at all magnetic observatories during the analyzed period. Correlations were strong to very strong (r > |0.80|) during the initial and main phases of the storm, and weaker to moderate durin g the recovery phase (|0.39| ≤ r ≤ |0.55|), revealing phase-dependent patterns. Comparison with the moderate period (24 March 2024) indicated similar r patterns between current and H-component to those observed during the initial and main storm phases (r < –0.91), but weak and inverse correlations between H-component and voltage (–0.10 ≤ r ≤ –0.16). Although preliminary, these results emphasize the importance of regional factors in GIC risk assessment and demonstrate the potential of integrating raw electrical TL data with geomagnetic observations for preventive strategies in power systems. Keywords: Power transmission lines; Pearson correlation; Equatorial electrojet; GICs. Observatorio Nacional Dissertação Tue, 07 Oct 2025 00:00:00 GMT http://localhost:8080/tede/handle/tede/198 2025-10-07T00:00:00Z